Review of Research on Early Cambrian Phosphatized Quadrapyrgites

The metazoan Quadrapyrgites consists, from proximal to distal ends, of an oral area, a cone, a collar, and an apex from the Early Cambrian Fortunian Stage in Xixiang Zhangjiagou section, southern Shaanxi Province, South China. Three morphological types of the apex, the most characteristic feature of the taxon, are identified from hundreds of Quadrapyrgites specimens. The Quadrapyrgites growth zone is situated at the oral end, where 12 terminal lobes are generated, uplifted, enlarged, and evaginated to form a crest; A one-by-one of crest number from 2 to 13 has been recognized. The unique growth pattern and ontogenetic sequence refute a cubozoan or cycloneuralian affinity for Olivooides and Quadrapyrgites, and instead defend a coronate scyphozoan hypothesis. An embryonic development and ontogenetic sequence with embryo and crest is constructed.